<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
        var str = 'aaa'; //字符
        var num = 10; //数字
        var bol = true; //布尔
        var udf = undefined; //未定义
        var nul = null; //空
        console.log(typeof str);
        console.log(typeof num);
        console.log(typeof bol);
        console.log(typeof udf);
        console.log(typeof nul);
    </script>
</body>
</html>